Please, Make Yourself Comfortable!

There is a woman I work with, who doesn’t make much effort to get to know anyone. She hasn’t worked here very long, and I can’t seem to get a real good read on her. My impression of her is a woman who could easily be referred to as a “Ball Buster”. She is from the old school of thought where a woman had to fight and scrap her way to the top by being one of the boys. (which in some cases is still true today, glass ceiling anyone? Uneven wages?) I don’t know how long she thought I worked for another office in the building, even though I’m at all our office meetings. She was genuinely surprised when I told her that we did indeed work for the same company. There have been several times when she’s barreled her way into someone’s lunch hour, disrupting the lunch not only of the person she’s talking to, but also disrupting the lunch and conversations of everyone seated around that person. It IS their lunch after all, and I think we can all agree that for the period of our lunch we should be absolved of having work–related conversation thrust upon us. She doesn’t even give the cursory, “I hate to interrupt your lunch, but….” She also “pops in” to offices when other people are there already. Actually, she pushes her way in. Shoving aside anyone else who is there having a conversation. I’ve experienced this first hand. More than once. And I’ve just about had enough of it. Take today for instance. I was in my friend’s office, which does happen to be located next to Mrs. B.Buster, chatting about life, and work when Mrs. B.Buster appears in the doorway, notepad and pen in hand. “OH! I need to talk to my friend! How are you?” as she slides by me (I was standing by my friend’s desk) and plops herself in the “guest” chair. My friend turns from me, to her, “Oh fine.”
“Do you guys have a meeting?” I asked, knowing full well they didn’t because my friend had just finished telling me she wondered why she’d even bothered to come back from a meeting held off “campus”.
“We do, she just doesn’t know it yet.” Says Mrs. B.Buster, without even bothering to glance my way.
“Ooooh?” my friend giggles surprised and a tad uncomfortable because of this sudden development.
“Yes! I need something from YOU.” Demands Mrs. B.Buster.
“Well. I guess I’ll leave you to it then.” I say to them both and then turn directly to my friend and say pointedly, “We’ll finish this conversation later.”
As I turn to leave Mrs. B.Buster has already started in on their “meeting.”

I was a bit miffed as I made my way back to my desk. I was only in my friend’s office for maybe 10 minutes and I wasn’t having a loud, inappropriate conversation. I do keep my voice down because I know rather well how sound carries in this place. So I highly doubt we were disturbing her. She seems to have no clue when it comes to unwritten office etiquette. I’m quite done with her behavior, but I don’t know how to tell her to knock it the hell off. Normally I would say something trenchant; however she just so happens to be one of the Big Boss’ "people", so pissing her off is not a good idea.
What to do, oh WHAT TO DO?